1. Field of the Invention
The present invention generally relates to an X-ray computerized tomographic imaging apparatus. More specifically, the present invention is directed to X-ray CT imaging data acquisition circuitry with employment of a digital data bus.
2. Description of the Prior Art
In a typical X-ray CT (computerized tomographic) imaging system, as partially shown in FIG. 1, a large number of X-ray detectors Ch.sub.1 to CH.sub.n ("n" being an integer) are arranged around a biological body 2 under medical examination so as to detect fan-shaped X-rays 4 penetrated through the biological body 2. These X-rays 4 are emitted from an X-ray tube 1. These X-ray detectors Ch.sub.1 to CH.sub.n constitute an X-ray detecting unit 5.
X-ray signals derived from the respective X-ray detectors CH.sub.1 to CH.sub.n are integrated by corresponding integrators 10.sub.1 to 10.sub.n, and thereafter the integrated X-ray signals are held by corresponding sample-holds 12.sub.1 to 12.sub.n. Then, the integrated X-ray signals are supplied to a multiplexer 14. As a result, for instance, the integrated X-ray signal derived from the first X-ray detecting channel (detector CH.sub.1) is outputted from the multiplexer 14 to an A/D converter 16 via an analog data bus (signal channels) 15. Subsequently, the digital X-ray signal (data) is supplied via a data coupler 18A to a computer system (not shown in detail) in which image reconstruction and other data processing are carried out so as to obtain X-ray CT image data of a slice of the biological body 2.
Similarly, the X-ray signals are supplied by the multiplexer 14, via the analog data bus 15 and A/D converter 16, to the computer system in order to similarly acquire X-ray CT image data of the slice by way of the image reconstruction technique.
The above described X-ray CT imaging system is known in the medical electronics field from, for instance, Japanese patent Disclosure (KOKAI) Application No. 2-191438 (opened on Jul. 27, 1990) filed by Toshiba corporation, and also "Radiology of the skull and brain TECHNICAL ASPECTS OF COMPUTED TOMOGRAPHY" page 4152, FIG. 119-21, volume 5, 1981, by T. H. Newton and G. D. Potts, the C. V. Mosby Company, LONDON.
As previously described, the multiplexer 14 multiplexes the respective X-ray signal detector/processing channels Ch.sub.1 -CH.sub.n ; 10.sub.1 -10.sub.n and 12.sub.1 -12.sub.n so as to sequentially furnish the respective X-ray signals, via the A/D converter 16 and the data coupler 18A, to the computer system. When, for instance, the multiplexer 14 is operated to receive the X-ray image signal from the first X-ray signal detector/processing channel Ch.sub.1, 10.sub.1 `and 12.sub.1, and then to supply thermal image X-ray signal to the A/D converter 16. As ready seen from a waveform diagram of FIG. 2, such a switching operation may cause a "long transition phenomenon". To obtain the first X-ray image signal in a stable condition, it will normally take a time period of 5 to 6 microseconds, which impedes high speed X-ray image data acquisition.
On the other hand, it is known in the art that the packaging density of X-ray detectors should be increased in order to realize a multislice or volume type X-ray CT system. Accordingly, a total image data acquisition time period of this multislice type X-ray CT system is prolonged, as compared with the normal X-ray CT system, due to the above-explained long transition time.
Furthermore, since the analog signal data bus 15 is employed between the output of the multiplexer 14 and the input of the A/D converter 16, noises may be induced into the X-ray image signals transferred from the multiplexer 14 to the A/D converter 16, resulting in deterioration of X-ray CT image quality.